From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41779) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1euDtz-0008AR-OE for qemu-devel@nongnu.org; Fri, 09 Mar 2018 04:01:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1euDty-0008Da-Pz for qemu-devel@nongnu.org; Fri, 09 Mar 2018 04:01:23 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39642 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1euDty-0008DE-KC for qemu-devel@nongnu.org; Fri, 09 Mar 2018 04:01:22 -0500 From: Peter Xu Date: Fri, 9 Mar 2018 16:59:55 +0800 Message-Id: <20180309090006.10018-13-peterx@redhat.com> In-Reply-To: <20180309090006.10018-1-peterx@redhat.com> References: <20180309090006.10018-1-peterx@redhat.com> Subject: [Qemu-devel] [PATCH v8 12/23] monitor: let suspend_cnt be thread safe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , "Daniel P . Berrange" , Paolo Bonzini , Fam Zheng , Juan Quintela , mdroth@linux.vnet.ibm.com, peterx@redhat.com, Eric Blake , Laurent Vivier , Markus Armbruster , marcandre.lureau@redhat.com, "Dr . David Alan Gilbert" Monitor code now can be run in more than one thread. Let it be thread safe when accessing suspend_cnt counter. Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Signed-off-by: Peter Xu --- monitor.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/monitor.c b/monitor.c index 6959e963e2..71b696c8f3 100644 --- a/monitor.c +++ b/monitor.c @@ -194,7 +194,7 @@ struct Monitor { CharBackend chr; int reset_seen; int flags; - int suspend_cnt; + int suspend_cnt; /* Needs to be accessed atomically */ bool skip_flush; bool use_io_thr; @@ -3816,7 +3816,7 @@ static int monitor_can_read(void *opaque) { Monitor *mon = opaque; - return (mon->suspend_cnt == 0) ? 1 : 0; + return !atomic_mb_read(&mon->suspend_cnt); } /* @@ -3948,7 +3948,7 @@ int monitor_suspend(Monitor *mon) { if (!mon->rs) return -ENOTTY; - mon->suspend_cnt++; + atomic_inc(&mon->suspend_cnt); return 0; } @@ -3956,8 +3956,9 @@ void monitor_resume(Monitor *mon) { if (!mon->rs) return; - if (--mon->suspend_cnt == 0) + if (atomic_dec_fetch(&mon->suspend_cnt) == 0) { readline_show_prompt(mon->rs); + } } static QObject *get_qmp_greeting(Monitor *mon) @@ -4022,19 +4023,19 @@ static void monitor_event(void *opaque, int event) monitor_resume(mon); monitor_flush(mon); } else { - mon->suspend_cnt = 0; + atomic_mb_set(&mon->suspend_cnt, 0); } break; case CHR_EVENT_MUX_OUT: if (mon->reset_seen) { - if (mon->suspend_cnt == 0) { + if (atomic_mb_read(&mon->suspend_cnt) == 0) { monitor_printf(mon, "\n"); } monitor_flush(mon); monitor_suspend(mon); } else { - mon->suspend_cnt++; + atomic_inc(&mon->suspend_cnt); } qemu_mutex_lock(&mon->out_lock); mon->mux_out = 1; -- 2.14.3